Apparatus and method for sequestering flue gas co2

ABSTRACT

A fluidized bed reactor device for sequestering flue gas CO 2  from a flue gas source is provided. The fluidized bed reactor device comprises an operating portion having a first end and a second end. A flue gas inlet is formed at the first end of the operating portion with the flue gas inlet receiving flue gas from the flue gas source. A flue gas outlet formed at the second end of the operating portion. A distributor plate is mounted within the operating portion adjacent the first end of the operating portion. A volume of fly ash is encased within the operating portion between the second end and the distributor plate with the flue gas traveling through the distributor plate and the fly ash creating reacted flue gas wherein the reacted flue gas exits the operating portion through the flue gas outlet.

The present application is a continuation of International ApplicationPCT/US2006/049411, with an international filing date of Dec. 28, 2006,which claims benefit of priority of pending provisional patentapplication Ser. No. 60/755,959, filed on Jan. 3, 2006, entitled “Methodfor Sequestering Flue Gas CO₂”.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to an apparatus and method forsequestering flue gas CO₂ and, more particularly, the invention relatesto an apparatus and method for sequestering flue gas CO₂ having afluidized bed reactor for simultaneously capturing and mineralizing coalcombustion flue gas CO₂,

2. Description of the Prior Art

Atmospheric CO₂ (g) is indispensable for physical, chemical, andbiological processes which occur in the atmosphere, hydrosphere, andgeosphere of the planet Earth. During the past 150 years, atmosphericCO₂ concentration increased approximately 30 percent, due to burning offossil fuels containing carbon. For example, before industrial rapidgrowth, the atmospheric CO₂ concentration was 280 ppm and the currentCO₂ concentration is 381 ppm. Increase in atmospheric CO₂ concentrationis typically attributed to the global warming and subsequent climatechange problems.

Coal reserves are vital for providing global primary energy needs.Studies suggest that energy production from coal combustion process isalso recognized for more than 50% of the increase in global CO₂ levelsin the atmosphere. Energy production from coal combustion power plants,like any other industrial process, results in various by-products,including flue gases (e.g., CO₂, SOx, NOx) and solid wastes (e.g., flyash and bottom ash). The new Clean Air Act enacted by the U.S. Congressmandated the reduction of SOx emissions from coal burning power plants.As a result, varieties of Clean Coal Technologies (CCTs) are developedand implemented. Applications of CCTs result in production of alkalineCCT ash with pH ranging from 9-12. In addition, there has been muchdiscussion recently on proposals to reduce atmospheric CO₂ emissions,possibly by enacting carbon taxes.

Currently several techniques exist to capture CO₂ from coal combustionprocesses:

-   -   Pre-combustion methods (fuel decarbonization);    -   Combustion in O₂/CO₂ atmospheres (oxy-fuel firing); and    -   Post-combustion capture methods.        However, all of the above techniques have their own drawbacks.        For example, these techniques are energy extensive and produce        additional by-products which require special handling and        disposal methods.

Several journal articles on the CO₂ (g) infusion technique (carbonationprocess) for alkaline solid wastes have been published. Thesecarbonation studies were conducted in an attempt to speed up the naturalcarbonation process as well help protect the environment (air, surfacewater, soil, and groundwater). The studies suggested that since thecarbonation process uses CO₂, which can be obtained from the coalcombustion process itself. Another potential benefit is that thecarbonation process could help capture and minimize CO₂ emissions intothe atmosphere. However, previous batch laboratory experiments haveexperienced diffusion limitations—that is, the CO₂ may not efficientlycontact the ash sample. In addition, nothing exists to simultaneouslycapture and mineralize coal combustion flue gas CO₂ with fly ash orbottom ash under actual plant combustion conditions.

Accordingly, there exists a need for an in-plant use to capture andmineralize flue gas CO₂ for both reducing flue gas CO₂ emissions andstabilizing ash.

SUMMARY

The present invention is a fluidized bed reactor device for sequesteringflue gas CO₂ from a flue gas source. The fluidized bed reactor devicecomprises an operating portion having a first end and a second end. Aflue gas inlet is formed at the first end of the operating portion withthe flue gas inlet receiving flue gas from the flue gas source. A fluegas outlet formed at the second end of the operating portion. Adistributor plate is mounted within the operating portion adjacent thefirst end of the operating portion. A volume of fly ash is encasedwithin the operating portion between the second end and the distributorplate with the flue gas traveling through the distributor plate and thefly ash creating reacted flue gas wherein the reacted flue gas exits theoperating portion through the flue gas outlet.

In addition, the present invention includes a method for sequesteringflue gas CO₂ from a flue gas source for simultaneously capturing andmineralizing coal combustion flue gas CO₂. The method comprisesproviding an operating portion having a first end and a second end,forming a flue gas inlet at the first end of the operating portion,forming a flue gas outlet at the second end of the operating portion,mounting a distributor plate within the operating portion adjacent thefirst end of the operating portion, encasing a volume of fly ash withinthe operating portion between the second end and the distributor plate,introducing flue gas from the flue gas source into the operating portionthrough the flue gas inlet, forcing the flue gas through the distributorplate, forcing the flue gas through the volume of fly ash creatingreacted flue gas, separating the fly ash from the reacted flue gas, andremoving the reacted flue gas from the operating portion through theflue gas outlet.

The present invention further includes a fluidized bed reactor devicefor sequestering flue gas CO₂ from a flue gas source. The fluidized bedreactor device comprises an operating portion having a first end and asecond end. A flue gas inlet is formed at the first end of the operatingportion, the flue gas inlet receiving flue gas from the flue gas source.A flue gas outlet is formed at the second end of the operating portion.A distributor plate is mounted within the operating portion adjacent thefirst end of the operating portion. A volume of fly ash is encasedwithin the operating portion between the second end and the distributorplate with the flue gas traveling through the distributor plate and thefly ash creating reacted flue gas. Pressurizing means between theoperating portion and the flue gas source force the flue gas from theflue gas source through the operating portion from the first end to thesecond end. Filtering means mounted over the flue gas outlet filtersreacted flue gas from fly ash with the reacted flue gas exiting theoperating portion through the flue gas outlet wherein the reacted fluegas exits the operating portion through the flue gas outlet and whereinthe fluidized bed reactor simultaneously captures and mineralizes coalcombustion flue gas CO₂.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating a fluidized bed reactor forsimultaneously capturing and mineralizing coal combustion flue gas CO₂,constructed in accordance with the present invention; and

FIG. 2 is a graph illustrating the effect of coal combustion flue gas oninorganic carbon content of fly ash samples.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As illustrated in FIG. 1, the present invention is an apparatus andmethod for sequestering flue gas CO₂, indicated generally at 10, whichsimultaneously captures and mineralizes coal combustion flue gas CO₂from a flue gas source such as a power plant stack. The apparatus 10 ofthe present invention includes a fluidized bed reactor 12 designed andfabricated to simultaneously capture and mineralize coal combustion fluegas CO₂. The fluidized bed reactor 12 is preferably constructed from aPlexiglas material allowing the fluidized bed operation to be observed.While the fluidized bed reactor 12 has been described and illustratedherein as being constructed from a Plexiglas material, it is within thescope of the present invention to construct the fluidized bed reactor 12from other materials.

Since flue gas from a power plant stack is available at approximatelyatmospheric pressure and does not provide sufficient pressure to operatethe fluidized bed reactor 12, the apparatus 10 of the present inventionincludes a blower 14 (preferably approximately sixty (60) standard cubicfeet per minute) forcing the flue gas through the fluidized bed reactor12. The blower 14 includes a flue gas inlet 16 for receiving flue gasfrom the flue gas source and flue gas outlet 18 for directing thepressurized flue gas to the fluidized bed reactor 12.

The fluidized bed reactor 12 of the apparatus 10 of the presentinvention has an operating portion 20 having a first end 22 and a secondend 24. The operating portion 20 is preferably cylindrical having anapproximately one (1′) foot diameter and an approximately four (4′) feetlong length although having an operating portion 20 with a differentshape, diameter/width, and/or length is within the scope of the presentinvention. A flue gas inlet 26 is positioned near the first end 22 ofthe operating portion 20 of the fluidized bed reactor 12 for receivingthe pressurized flue gas from the blower 14.

The operating portion 20 of the fluidized bed reactor 12 furthercontains a volume of fly ash encased therein. Preferably, the volume offly ash has a depth of approximately two (2′) feet. A distributor plateor screen 30 is mounted within the operating portion 20 directly belowthe volume of fly ash. The distributor plate 20 preferably includesthree hundred and seven (307) one-eighth (⅛″) inch diameter holesproviding uniform distribution of the pressurized flue gas through thevolume fly ash directly above the distributor plate 20. It should benoted that the number and size of the holes in the distributor plate 20can be varied depending on the desired distribution of the flue gas.

A pleated fabric filter 32 is secured to the first end 22 of theoperating portion 20 of the fluidized bed reactor 12. The filter 32separates the reacted flue gas and returns the fly ash to the volume offly ash for additional contact with fresh flue gas from the power plantstack. The reacted gas exits the operating portion 20 of the fluidizedbed reactor 12 through the flue gas outlet 28.

The fluidized bed reactor 12 of the apparatus 10 of the presentinvention further includes a temperature gauge 34 for measuring thetemperature within the operating portion 20 and a pressure gauge 36 formeasuring the pressure within the operating portion 20. The temperaturegauge 34 and the pressure gauge 36 allow constant monitoring of thefluidized bed reactor 12 during operation.

Testing

The fluidized bed reactor has been tested at a typical coal combustionpower plant in Wyoming. In this field test, approximately one hundred(100 lbs.) of power plant fly ash were reacted with their respectiveflue gases for fifteen (15) minutes. Reacted and unreacted fly ashsamples were carefully transported to the Department of RenewableResources, University of Wyoming, for subsequent testing for inorganiccarbon content.

Results from field testing are illustrated in FIG. 2. These results showthat the inorganic carbon content of the fly ash increased by a factorof approximately thirty (30) times based on a calculation of theapproximate flow rate of flue gas, amount of ash in the reactor, and thelab results, thereby suggesting that ash absorbed about four (4%)percent of the CO₂ that passed through the reactor.

The apparatus and method of the present invention has many benefits.Several of the benefits are as follows:

-   -   Economically capturing flue gas CO₂ from coal combustion and        other combustion processes (e.g., cement plants, municpal sold        waste incinerators, and other solid waste incinerators) and        converting these greenhouse emissions into beneficial products.    -   Minimizing emissions of CO₂ and protecting the atomosphere from        coal combustion power plants, cement plants, municipal solid        waste incinerators, and other solid waste incinerators.    -   Stabilizing carbonated ash for safe land disposal or sale for        other uses, such as immobilizing contaminants at hazardous waste        disposal sites, and reclamation of acidic and sodic soils.

The foregoing exemplary descriptions and the illustrative preferredembodiments of the present invention have been explained in the drawingsand described in detail, with varying modifications and alternativeembodiments being taught. While the invention has been so shown,described and illustrated, it should be understood by those skilled inthe art that equivalent changes in form and detail may be made thereinwithout departing from the true spirit and scope of the invention, andthat the scope of the present invention is to be limited only to theclaims except as precluded by the prior art. Moreover, the invention asdisclosed herein, may be suitably practiced in the absence of thespecific elements which are disclosed herein.

1-20. (canceled)
 21. A fluidized bed reactor for sequestering flue gasCO₂ from a flue gas source, comprising: an operating portion having afirst end and a second end; a flue gas inlet formed at the first end ofthe operating portion, the flue gas inlet receiving flue gas from theflue gas source; a flue gas outlet formed at the second end of theoperating portion; a distributor plate mounted within the operatingportion adjacent to the first end of the operating portion; and fly asharranged within the operating portion between the second end and thedistributor plate, wherein the flue gas is configured to travel throughthe distributor plate and the fly ash is configured to react with theflue gas and mineralize a portion of CO₂ with the fly ash at a rate ofabout 0.05 [grams of CO₂/(min.*kg of flyash)] or greater.
 22. Theapparatus of claim 21, wherein the operating portion comprises a plasticmaterial.
 23. The apparatus of claim 21, wherein the operating portioncomprises a cylindrical shape.
 24. An apparatus for sequestering fluegas CO₂ from a flue gas source, comprising: an operating portion havinga first end and a second end; a flue gas inlet formed at the first endof the operating portion, the flue gas inlet configured to receive fluegas from the flue gas source; a flue gas outlet formed at the second endof the operating portion; a distributor plate mounted within theoperating portion adjacent to the first end of the operating portion; apump arranged between the operating portion and the flue gas sourceconfigured to provide the flue gas from the flue gas source through theoperating portion from the first end to the second end at apredetermined pressure; and fly ash encased within the operating portionbetween the second end and the distributor plate, wherein the flue gasis configured to travel through the distributor plate and the fly ashand the apparatus is configured to simultaneously capture and mineralizea portion of the CO₂ in the flue gas at a rate of about 0.05 [grams ofCO₂/(min.*kg of flyash)] or greater.
 25. The fluidized bed reactor ofclaim 24, wherein the operating portion comprises a transparentmaterial.
 26. The fluidized bed reactor of claim 24, wherein thedistributor plate comprises a plurality of holes configured to provideuniform distribution of the pressurized flue gas through at least aportion of the fly ash.
 27. The fluidized bed reactor of claim 26,further comprising: a filtering mounted at the flue gas outletconfigured to filter flue gas from fly ash.
 28. The fluidized bedreactor of claim 27, wherein the filter comprises a pleated fabricfilter.
 29. The fluidized bed reactor of claim 24, further comprising: atemperature gauge for measuring the temperature within the operatingportion; and a pressure gauge for measuring the pressure within theoperating portion.
 30. A method using a fluidized bed reactor forsequestering CO₂ from a flue gas, comprising the steps of: providingindustrial flue gas comprising carbon dioxide to the fluidized bedreactor; and mineralizing at least a portion of the carbon dioxide byreacting the carbon dioxide with unprocessed power plant fly ash to formcarbonated ash in the fluidized bed reactor at a rate of about 0.05[grams of CO₂/(min.*kg of flyash)] or greater.
 31. The method of claim30, wherein the industrial flue gas comprises a flue gas from a solidwaste incinerator.
 32. The method of claim 30, wherein the industrialflue gas comprises a flue gas from a coal combustion source.
 33. Themethod of claim 30, wherein the industrial flue gas comprises a flue gasfrom a cement plant.
 34. The method of claim 30, wherein the unprocessedpower plant fly ash comprises bottom ash.
 35. The method of claim 30,further comprising the step of stabilizing the carbonated ash.
 36. Themethod of claim 30, further comprising the step of filtering the reactedflue gas with a filter to separate the reacted flue gas and return thefly ash for additional contact with the flue gas.
 37. The method ofclaim 30, wherein the step of providing the industrial flue gascomprises distributing the flue gas in a substantially uniformdistribution in the fluidized bed reactor.
 38. A method using afluidized bed reactor for simultaneously capturing and mineralizing CO₂in flue gas, the method comprising the steps of: providing the flue gascomprising the CO₂ to an inlet of the fluidized bed reactor;distributing the flue gas in a substantially uniform distribution in thefluidized bed reactor; simultaneously capturing and mineralizing CO₂ byreacting the flue gas with unprocessed power plant fly ash, wherein thesimultaneously capturing and mineralizing is conducted at a rate ofabout 0.05 [grams of CO₂/(min.*kg of flyash)] or greater; filtering thereacted flue gas and the fly ash to separate the reacted flue gas andreturn the fly ash for additional contact with the flue gas; andstabilizing the mineralized CO₂.
 39. The method of claim 38, wherein thedistributing step comprises providing flue gas at about 60 standardcubic feet per minute through a distributor plate.
 40. The method ofclaim 38, further comprising the steps of: measuring a temperaturewithin the fluidized bed reactor; and measuring the pressure within thefluidized bed reactor.
 41. The method of claim 38, wherein the flue gascomprises a flue gas from a solid waste incinerator.
 42. The method ofclaim 38, wherein the flue gas comprises a flue gas from a coalcombustion source.
 43. The method of claim 38, wherein the flue gascomprises a flue gas from a cement plant.
 44. The method of claim 38,wherein the fly ash comprises power plant fly ash.
 45. The method ofclaim 38, wherein the fly ash comprises bottom ash.
 46. A method using afluidized bed reactor for simultaneously capturing and mineralizing CO₂in flue gas of a coal fired plant, the method comprising the steps of:providing the flue gas from the coal fired plant to an inlet of thefluidized bed reactor; distributing the flue gas in a substantiallyuniform distribution in the fluidized bed reactor; simultaneouslycapturing and mineralizing CO₂ by reacting flue gas with the unprocessedpower plant fly ash to capture carbon dioxide at a rate of about 0.05[grams of CO₂/(min.*kg of flyash)] or greater; filtering the reactedflue gas and the fly ash; and stabilizing the reacted fly ash comprisingmineralized CO₂.
 47. The method of claim 46, wherein the flue gascomprises a flue gas from a coal combustion source.